Cast Iron Steak Tips with Mushroom-Onion Gravy

Ingredients

• 2 pounds sirloin steak tips, trimmed and cut into 1 1/2-inch pieces
• Salt
• pepper
• 1/4 cup vegetable oil
• 1 pound white mushrooms s, trimmed and sliced 1/4 inch thick
• 1 large onion, halved and sliced thin
• 2 garlic cloves, minced
• 2 teaspoons tomato paste
• 1/4 teaspoon minced fresh thyme or 1/4 teaspoon dried
• 3 tablespoons all-purpose flour
• 1 3/4 cups beef broth
• 1 tablespoon Worcestershire sauce
• 1 tablespoon chopped fresh parsley
• 2 teaspoons red wine vinegar